My rear blinker works at will, but it is not reliable. Had the problem diagnosed by dealership after my mechanic couldn’t figure out the problem. Dealership says it’s the integration relay, and they’ll be happy to fix for $600. Is this the ONLY possibility?

Get another opinion. I’ve never heard of an “integration relay,” but that doesn’t mean there isn’t one. What does this relay integrate, I wonder? Perhaps someone else can explain it. I’d ask an independent mechanic.